Note: Descriptions are shown in the official language in which they were submitted.
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DOUBLE-ACTING SHOCK DAMPER FOR A DOWNHOLE ASSEMBLY
BACKGROUND
Field of the Invention
[0001] The invention relates generally to downhole tools. More particularly,
the invention
relates to shock dampers for absorbing and damping impact loads generated by
jars and other
downhole force creating devices.
Background of the Technology
[0002] In oil and gas well operations, it is frequently necessary to apply an
axial blow to a
tool or tool string that is positioned downhole. For example, application of
axial force to a
downhole string may be desirable to dislodge drilling or production equipment
that is stuck in a
wellbore. Another circumstance involves the retrieval of a tool or string
downhole that has been
separated from its pipe or tubing string. The separation between the pipe or
tubing and the
stranded tool¨or fish¨may be the result of structural failure or a deliberate
disconnection
initiated from the surface. Another example of creating force in downhole
operations is with the
use of casing perforation tools.
[0003] As an example, jars have been used in petroleum well operations for
several decades to
enable operators to deliver axial impacts to stuck or stranded tools and
strings. Drilling jars are
frequently employed when either drilling or production equipment gets stuck in
the well bore.
The drilling jar is normally placed in the pipe string in the region of the
stuck object and allows
an operator at the surface to deliver a series of impact blows to the drill
string via manipulation
of the drill string. These impact blows are intended to dislodge the stuck
object, thereby
enabling continued downhole operations. Fishing jars are inserted into the
well bore to
retrieve a stranded tool or fish. Fishing jars are provided with a mechanism
that is designed
to firmly grasp the fish so that the fishing jar and the fish may be lifted
together from the well.
Many fishing jars are also provided with the capability to deliver axial blows
to the fish to
facilitate retrieval.
[0004] Conventional jars typically include an inner mandrel disposed in an
outer housing. The
mandrel is permitted to move axially relative to the housing and has a hammer
formed thereon,
while the housing includes an anvil positioned adjacent to the mandrel hammer.
By
impacting the anvil with the hammer at a relatively high velocity, a
substantial jarring force is
imparted to the stuck drill string. If the jarring force is sufficient, the
stuck string will be
dislodged and freed. However, while the jarring force may be sufficient to
dislodge the stuck
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string, the force may be so large as to damage the remaining components of the
downhole tool if
too much force is transferred to the other components.
[0005] Accordingly, there remains a need in the art for apparatus and methods
for applying
axial blows to downhole tools without damaging the downhole tools or other
components
coupled to such downhole tools.
BRIEF SUMMARY OF THE DISCLOSURE
[0006] These and other needs in the art are addressed in one embodiment by a
downhole
assembly. In an embodiment, the downhole assembly comprises a downhole tool.
In
addition, the downhole assembly comprises a downhole force-creating device.
Further, the
downhole assembly comprises a shock damper for the force generated from the
force-creating
device. The shock damper includes an outer housing having a central axis, a
first end, and a
second end opposite the first end. The outer housing includes a first annular
housing
shoulder axially positioned proximal the first end of the outer housing and a
second annular
housing shoulder axially positioned proximal the second end of the outer
housing. Each
annular housing shoulder extends radially inward from the outer housing. The
shock damper
also includes a mandrel located at least partially within the outer housing.
The mandrel
having a first end and a second end opposite the first end. The mandrel
includes a first
annular mandrel shoulder axially proximal the first end of the mandrel and a
second annular
mandrel shoulder axially proximal the second end of the mandrel. Each annular
mandrel
shoulder extends radially outward from the mandrel. Still further, the shock
damper includes
an annular cavity radially disposed between the outer housing and the mandrel
and axially
disposed between the housing shoulders and the mandrel shoulders. Moreover,
the shock
damper includes a spring disposed in the annular cavity. The mandrel is
configured to move
axially relative to the housing between an expanded position and a compressed
position. The
spring is configured to be compressed between one of the housing shoulders and
one of the
mandrel shoulders as the mandrel moves between the expanded and compressed
positions,
the compression of the spring resisting relative axial movement between the
mandrel and the
housing.
[0007] These and other needs in the art are addressed in another embodiment by
a method of
dampening the shock transferred to a downhole assembly. In an embodiment, the
method
comprises transferring the force from the shock to a mandrel located at least
partially inside a
hollow housing to move the mandrel relative to the housing between an expanded
position in
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one direction and to a compressed position in the other direction. The method
also comprises
resisting the movement of the mandrel between both the expanded position and
the
compressed position by compressing a spring to dampen the shock transferred to
the
downhole assembly.
[0008] These and other needs in the art are addressed in another embodiment by
a shock
damper for a downhole force-creating device. In an embodiment, the shock
damper
comprises a hollow housing having a central axis, a first end, and a second
end opposite the
first end. The housing includes an annular housing shoulder near each end of
the housing and
extending radially inward from the housing. In addition, the shock damper
comprises a
mandrel located at least partially inside the housing. The mandrel has a first
end and a
second end opposite the first end. The mandrel includes an annular mandrel
shoulder near
each end of the mandrel and extending radially outward from the mandrel.
Further, the shock
damper comprises a spring located in an annular cavity axially disposed
between the housing
and the mandrel housing, and radially disposed between the housing shoulders
and the
mandrel shoulders. The mandrel is configured to move axially relative to the
housing to an
expanded position in one direction and to a compressed position in the other
direction. The
spring is configured to be compressed between one of the housing shoulders and
one of the
mandrel shoulders as the mandrel moves between the expanded and compressed
positions,
the compression of the spring resisting relative movement between the mandrel
and the
housing and absorb the force moving the mandrel.
[0009] Embodiments described herein comprise a combination of features and
advantages
intended to address various shortcomings associated with certain prior
devices, systems, and
methods. The foregoing has outlined rather broadly the features and technical
advantages of
the invention in order that the detailed description of the invention that
follows may be better
understood. The various characteristics described above, as well as other
features, will be
readily apparent to those skilled in the art upon reading the following
detailed description,
and by referring to the accompanying drawings. It should be appreciated by
those skilled in
the art that the conception and the specific embodiments disclosed may be
readily utilized as
a basis for modifying or designing other structures for carrying out the same
purposes of the
invention. It should also be realized by those skilled in the art that such
equivalent
constructions do not depart from the spirit and scope of the invention as set
forth in the
appended claims.
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BRIEF DESCRIPTION OF THE DRAWINGS
[0010] For a detailed description of the preferred embodiments of the
invention, reference
will now be made to the accompanying drawings in which:
[0011] Figure 1 is a schematic side view of a downhole assembly including an
embodiment
of a double-acting shock damper for a downhole force-creating device in
accordance with the
principles described herein;
[0012] Figure 2 is a cross-sectional view of the double-acting shock damper of
Figure 1 with
the mandrel in the neutral position;
[0013] Figure 3 is a cross-sectional view of the double-acting shock damper of
Figure 1 with
the mandrel in the expanded position; and
[0014] Figure 4 is a cross-sectional view of the double-acting shock damper of
Figure 1 with
the mandrel in the compressed position.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0015] The following discussion is directed to various embodiments of the
invention.
Although one or more of these embodiments may be preferred, the embodiments
disclosed
should not be interpreted, or otherwise used, as limiting the scope of the
disclosure, including
the claims. In addition, one skilled in the art will understand that the
following description
has broad application, and the discussion of any embodiment is meant only to
be exemplary
of that embodiment, and not intended to intimate that the scope of the
disclosure, including
the claims, is limited to that embodiment.
[0016] Certain terms are used throughout the following description and claims
to refer to
particular features or components. As one skilled in the art will appreciate,
different persons
may refer to the same feature or component by different names. This document
does not
intend to distinguish between components or features that differ in name but
not function.
The drawing figures are not necessarily to scale. Certain features and
components herein
may be shown exaggerated in scale or in somewhat schematic form and some
details of
conventional elements may not be shown in interest of clarity and conciseness.
[0017] In the following discussion and in the claims, the terms "including"
and "comprising"
are used in an open-ended fashion, and thus should be interpreted to mean
"including, but not
limited to... . "Also, the term "couple" or "couples" is intended to mean
either an indirect or
direct connection. Thus, if a first device couples to a second device, that
connection may be
through a direct connection, or through an indirect connection via other
devices, components,
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and connections. In addition, as used herein, the terms "axial" and "axially"
generally mean
along or parallel to a central axis (e.g., central axis of a body or a port),
while the terms
"radial" and "radially" generally mean perpendicular to the central axis. For
instance, an
axial distance refers to a distance measured along or parallel to the central
axis, and a radial
distance means a distance measured perpendicular to the central axis. Any
reference to up or
down in the description and the claims will be made for purposes of clarity,
with "up",
"upper", "upwardly" or "upstream" meaning toward the surface of the borehole
and with
"down", "lower", "downwardly" or "downstream" meaning toward the terminal end
of the
borehole, regardless of the borehole orientation.
[0018] Referring now to Figure 1, a downhole assembly 10 is shown disposed in
a borehole
11 extending from the surface through an earthen formation. The borehole 11
includes a
casing 14 that extends downhole from the surface. In this embodiment, the
assembly 10 is
lowered downhole with a wireline string 20 extending from the surface through
the casing 14.
However, in general, the downhole assembly (e.g., assembly 10) can be run
downhole by any
suitable means including, without limitation, a pipe string, a slickline, a
drill string, a sucker
rod, or other suitable device. The assembly 10 includes one or more downhole
tools 30 for
performing downhole operations. In general, the tools 30 may include any
suitable tool(s) for
performing downhole operations including, without limitation, formation
testing tools,
perforation equipment, fracturing tools, fishing tools, etc.
[0019] As may be necessary to traverse particular production zones in the
formation, the
borehole 11 may include generally straight sections (vertical and/or
horizontal) and curved
sections. In reality, both straight and curved sections may include various
kinks and twists,
which increase the probability of the assembly 10 becoming lodged or stuck
downhole.
Consequently, in this embodiment, the assembly 10 includes a downhole force-
creating
device 100 coupled to the tool 30. In this embodiment, device 100 is ajar, and
thus, may also
be referred to as jar 100. In the event the assembly 10 becomes stuck in the
borehole 11, the
jar 100 can be triggered or fired to provide an abrupt, axial force sufficient
to dislodge the
assembly 10. In general, the jar 100 can be any jar known in the art. Although
the device
100 is a jar in this embodiment, in general, any suitable downhole force-
creating device can
be used in as force-creating device 100 in the assembly 10. Other examples of
suitable
downhole force-creating devices include items such as perforation guns for use
in casing
perforation operations.
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[0020] While the abrupt, axial force provided by the jar 100 is helpful to
dislodge the
downhole assembly 10 from being stuck, the force transferred to the remainder
of the
downhole assembly 10 might damage other components therein. However, in this
embodiment, the downhole assembly 10 also includes a shock damper 200 to
dampen the
force transferred to the other assembly components. The shock damper 200 is
coupled to the
jar 100 and in this embodiment, is positioned between the wireline 20 and the
jar 100.
However, in general, the shock damper 200 can be positioned at other locations
along the
assembly 10. As will be described in more detail below, when the jar 100
triggers or fires,
the shock damper 200 dampens the force transmitted from the jar 100 to the
remainder of the
downhole assembly 10, thereby offering the potential to protect such
components from
impact damage and shock.
[0021] Referring now to Figure 2, the shock damper 200 of assembly 10 is
shown. The
shock damper 200 placed in-line with and coupled to the other components that
make up the
assembly 10. In this embodiment, the shock damper 200 includes a hollow,
generally tubular
outer housing 210 and a tubular mandrel 212 disposed within the housing 210.
Both the
housing 210 and the mandrel 212 are connected to the other components in the
assembly 10
while still allowing the mandrel 212 to move relative to the housing 210. As
will be
described in more detail below, the mandrel 212 can be moved axially relative
to the housing
210 between a neutral run-in position (Figure 2), an expanded position (Figure
3) with the
mandrel 212 moved axially upward/uphole relative to the neutral position, and
a compressed
position (Figure 4) with the mandrel 212 moved axially downward/downhole
relative to the
neutral position. Shock damper 200 provides shock absorption and damping when
the
mandrel 212 transitions from the neutral position to both the expanded and
compressed
positions. In other words, the shock damper 200 provides shock absorption and
damping
when the mandrel 212 moves axially from the neutral position in either
direction relative to
the outer housing 210, and thus, may be described as "double-acting."
[0022] The housing 210 has a central or longitudinal axis 215, a first or
upper end 210a, a
second or lower end 210b, and a through passage or bore 213 extending axially
between ends
210a, b. An annular shoulder 214 is provided within the housing 210 proximal
each end
210a, b. The housing shoulder 214 positioned proximal the upper end 210a may
also be
referred to as the upper housing shoulder 214, and the housing shoulder 214
positioned
proximal the lower end 210b may also be referred to as the lower housing
shoulder 214.
Each housing shoulder 214 extends radially inward from the housing 210 towards
the
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mandrel 212. In this embodiment, the housing shoulders 214 are formed by
shoulder ends
216 sealingly attached to each end 210a, b of the housing 210, each shoulder
end 216 having
a smaller internal diameter than the housing 210. However, in other
embodiments, the
housing shoulders (e.g., shoulders 214) can be formed by other surfaces or
structures. For
example, the housing shoulders can be machined on the inner surface of the
housing (e.g.,
housing 210).
[0023] The mandrel 212 is coaxially aligned with the housing 210 and has a
first or upper
end 212a proximal the end 210a, a second or lower end 212b proximal the end
210b, and a
through passage or bore 217 extending axially between ends 212a, b. An annular
shoulder
220 is provided on the outside of the mandrel 212 proximal each end 212a, b.
The mandrel
shoulder 220 positioned proximal the upper end 212a may also be referred to as
the upper
mandrel shoulder 220, and the mandrel shoulder 220 positioned proximal the
lower end 212b
may also be referred to as the lower mandrel shoulder 220. Each mandrel
shoulder 220
extends radially outward from the mandrel 212 towards the housing 210. As
shown in Figure
2, the lower mandrel shoulder 220 is formed on the mandrel 212 itself and the
upper mandrel
shoulder 220 is formed by the lower end of a mandrel extension 222 attached to
the upper
end 212a of the mandrel 212. However, in other embodiments, the mandrel
shoulders (e.g.,
shoulders 220) can be formed by other surfaces or structures.
[0024] As shown in Figure 2, with the mandrel 212 in the neutral position, the
upper
shoulders 214, 220 are axially aligned and the lower shoulders 214, 220 are
axially aligned.
In addition, an adjustable annular chamber or cavity 211 is formed radially
between the
housing 210 and the mandrel 212, and axially between upper shoulders 214, 220
and lower
shoulders 214, 220. An annular spring 230 is disposed within the annular
cavity 211 and has
a first or upper end 230a and a second or lower end 230b. In this embodiment,
the spring 230
is a stack of Belleville springs. The spring 230 is designed to support the
weight of the
downhole assembly 200 while located downhole without being completely
compressed and
preferably biasing the shock damper 200 to the neutral position with the upper
shoulders 214,
220 axially aligned and the lower shoulders 214, 220 axially aligned. This
allows the spring
230 to compress in response to axial forces transferred to the mandrel 212 in
either direction
as described below.
[0025] A pair of annular pistons 240 are disposed in the annular cavity 211.
In particular, a
first or upper piston 240 is positioned in the annular cavity 211 between end
230a and the
upper shoulders 214, 220, and a second or lower piston 240 is disposed in the
annular cavity
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211 between the lower end 230b and the lower shoulders 214, 220. The annular
pistons 240
have a sufficient radial thickness to radially overlap with at least a portion
of the
corresponding shoulders 214, 220. In this embodiment, each annular piston 240
has a
radially width that is substantially the same as the radial with of the
annular cavity 211, and
thus, each annular piston 240 slidingly engages the housing 210 and the
mandrel 212 within
the cavity 211. Each piston 240 include annular seals that sealingly engage
the inside of the
housing 210 and the outside of the mandrel 212 to seal the annular cavity 211
between the
pistons 240.
[0026] The annular cavity 211 is fluid-filled and at least one piston 240
includes at least one
port 242 that controls the flow of fluid through the piston 240 and into and
out of the cavity
so as to affect the dynamic response of the spring 230. The port(s) 242 can
be, for example, a
JEVA orifice installed in the piston 240. The port(s) 242 allow fluid inside
the cavity to
balance with hydrostatic pressure. For example, the pressure in cavity 211 can
be balanced
with the hydrostatic pressure in the well with use of a balance piston
arrangement or other
means known in the art. In addition, the port(s) 242 enable the adjustment of
pressure in the
cavity 211 to accommodate fluid temperature changes. In this embodiment, at
least one
piston 240 includes at least one check valve 244 that allows one-way fluid
flow into the
cavity 211 but not out of the cavity 211. Preferably, between the two pistons
240, there is at
least one port 242 and one check valve 244, which can be provided in the same
piston 240 or
in different pistons 240. More than one port 242 and/or more than one check
valve 244 can
be provided in either piston 240 depending on the desired operating
characteristics of the
shock damper 200. For example, if the protected tools are subjected to
drilling jar impacts
while coupled to drill pipe from the surface the impact loads may be in the
range of 500,000
pounds (¨ 2,224,111 Newtons), which would necessitate an orifice with much
greater
restriction than the case of a wireline jar that may only create a 50,000
pound (¨ 222,411
Newton) impact load.
[0027] As shown in Figures 3 and 4, actuation of the jar 100 provides an
abrupt, axial force
to help dislodge the assembly 10. The force from the jar 100 is dampened as
the damper 200
restricts axial movement of the mandrel 212 relative to the housing 210 from
the neutral
position to both the expanded and compressed positions. In particular, when
the jar 100
actuates, the axial force is transferred to the mandrel 212 to move the
mandrel 212 towards
either the expanded position shown in Figure 3 (the mandrel 212 is moved
axially upward
relative to the housing 210 and the neutral position) or the compressed
position shown in
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Figure 4 (the mandrel 212 is moved axially downward relative to the housing
210 and the
neutral position). Movement of the mandrel 212 relative to the housing 210 in
either axial
direction (up or down) moves one of the mandrel shoulders 220 towards the
housing shoulder
214 on the opposite side of the spring 230. Since the pistons 240 radially
overlap with both
of the corresponding shoulders 214, 220, movement of one of the mandrel
shoulders 220
towards a housing shoulder 214 on the opposite side of the spring 230 also
moves the pistons
240 towards each other, thereby compressing the spring 230 and the fluid
within the annular
cavity 211. Thus, the spring 230 is compressed when the mandrel 212 is moved
axially in
either direction from the neutral position relative to the housing 210. At
least some of the
force from the jar 100 is thus used to compress the spring 230 through
movement of the
mandrel 212 relative to the housing 210.
[0028] Compression of the spring 230 absorbs some of the axial shock and
reduces the force
transferred to the rest of the components of the downhole tool 10. As the
mandrel 212 moves
relative to the housing 210 and compresses the spring 230, the potential
energy stored in the
spring 230 is eventually released, and urges the mandrel 212 in the opposite
axial direction.
Thus, once the initial force from the jar 100 is transferred to the mandrel
212, the spring 230
continues to move the mandrel 212 axially back and forth within the housing
210 between the
expanded and compressed positions shown in Figures 3 and 4 until the force is
dissipated
enough that the spring 230 is no longer compressed and the mandrel 212 returns
to its neutral
position shown in Figure 2. As the spring 230 is compressed and expanded
during movement
of the mandrel 212 within the housing 210, the pistons 240 move axially
towards and away
from each other, respectively. As the pistons 240 move axially toward each
other and the
volume of the cavity 211 is decreased, the fluid within the annular cavity 211
between the
pistons 240 is allowed to flow through port(s) 242. Flow through the port(s)
242 is restricted,
and thus, dampens the movement of the mandrel 212 relative to the housing 210.
The shock
damper 200 is thus able to be used repeatedly to absorb force from multiple
uses of the jar
100. It should be appreciated that as the pistons 240 move axially away from
each other and
the volume of the cavity 211 is increased, fluid is allowed to flow into the
cavity 211 through
the one-way check valve(s) 244.
[0029] While preferred embodiments have been shown and described,
modifications thereof
can be made by one skilled in the art without departing from the scope or
teachings herein.
The embodiments described herein are exemplary only and are not limiting. Many
variations
and modifications of the systems, apparatus, and processes described herein
are possible and
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are within the scope of the invention. For example, the relative dimensions of
various parts,
the materials from which the various parts are made, and other parameters can
be varied.
Accordingly, the scope of protection is not limited to the embodiments
described herein, but
is only limited by the claims that follow, the scope of which shall include
all equivalents of
the subject matter of the claims. Unless expressly stated otherwise, the steps
in a method
claim may be performed in any order. The recitation of identifiers such as
(a), (b), (c) or (1),
(2), (3) before steps in a method claim are not intended to and do not specify
a particular
order to the steps, but rather are used to simplify subsequent reference to
such steps.
